Complex Impedance Moisture Sensor and Sensing Method

ABSTRACT

An insulated pipe includes an elongated tube having a first end, a second end, and a sidewall extending therebetween, including an inner surface and an outer surface. The insulated pipe also includes an insulating member covering a portion of the outer surface of the sidewall and a planar moisture sensor. The planar moisture sensor is positioned in the insulating member or between the insulating member and the outer surface of the tube sidewall. The planar moisture sensor includes: a first electrode having a flat conductive member having an inner surface and an outer surface; a second electrode spaced apart from the first electrode having a flat conductive member having an inner surface and an outer surface, and a dielectric layer. The dielectric layer includes an absorbent dielectric polymer material positioned between and in electrical contact with the inner surfaces of the first electrode and the second electrode.

FIELD OF THE INVENTION

This invention relates to devices having moisture sensors for sensingwhen moisture is present.

BACKGROUND OF THE INVENTION

Certain objects including, for example, building fixtures (e.g., pipes,insulation, electric wiring, and structural materials), vehicles (e.g.,automobiles, airplanes, helicopters, drones, and ships), electronicdevices (e.g., consumer appliances), and containers (e.g., storagetanks), include areas which should remain free from, or substantiallyfree from, moisture. Such structures may be covered by a moistureresistive coating or enclosed within a housing to restrict or preventingression of moisture. In some cases, collected moisture could damagecomponents contained within the housing or encapsulated by the coating.For example, electronic circuitry or components of electronic devices,such as consumer appliances, can be damaged when moisture leaks throughand accumulates in the device housing. Performance of buildingmaterials, such as insulation, wood framing, bricks, stone, vinylsiding, composite wood materials, and others can also be reduced due toprolonged exposure to moisture or standing water. For example, thermalresistance of insulation material can be reduced as the insulation isexposed to moisture. Metal or wooden building structural materials, suchas framing and beams, can degrade or corrode over and need to bereplaced. Prolonged exposure to standing water also allows mold to growon building structures or storage containers, which can damage thestructures and substances contained therein, as well as pose a healthrisk.

SUMMARY OF THE INVENTION

The invention includes an insulated pipe including an elongated tubecomprising a first end, a second end, and a sidewall extendingtherebetween; an insulating member at least partially enclosing aportion of the pipe sidewall, the insulating member comprising at leastone channel extending through at least a portion of the insulatingmember. The insulated pipe also includes at least one coaxial moisturesensor positioned within at least a portion of the channel configured tosense moisture in the channel. The at least one coaxial moisture sensorincludes: a dielectric member comprising a sleeve defining a center holeformed from an absorbent dielectric polymer material; an outer electrodeelectrically connected with an outer surface of the dielectric member,the outer electrode comprising a moisture permeable sleeve which permitsmoisture to pass to the dielectric member; and an inner electrodecomprising a wire extending through the center hole of and electricallyconnected with an inner surface of the dielectric member. The dielectricmember is in electrical contact with the first and second electrodes andmaintains the first and the second electrodes spaced from one another.

The invention also includes a container configured to enclose objects ina low moisture environment. The container includes: a top portion, abottom portion, and sides extending between the top portion and thebottom portion thereof. The container further includes at least onecoaxial moisture sensor enclosed within a cavity defined by the topportion, bottom portion, and sides. The at least one coaxial moisturesensor comprising: a dielectric member comprising a sleeve defining acenter hole formed from an absorbent dielectric polymer material; anouter electrode electrically connected with an outer surface of thedielectric member, comprising a porous sleeve for permitting moisture topass through the sleeve; and an inner electrode comprising a wireextending through the center hole of and electrically connected with aninner surface of the dielectric member. The dielectric member is inelectrical contact with the first and second electrodes and maintainsthe first and the second electrodes spaced from one another.

The invention also includes a method for detecting moisture ininsulation surrounding a pipe including: applying an alternatingelectrical current to a coaxial moisture sensor positioned within achannel extending through insulation at least partially surrounding apipe. The coaxial moisture sensor comprises: a dielectric membercomprising a sleeve defining a center hole formed from an absorbentpolymer material, a first electrode surrounding at least a portion ofthe dielectric member, and a second electrode extending through aportion of the center hole of the dielectric member. The method furtherincludes continually or periodically measuring a complex impedance ofthe dielectric polymer material with sensor electronics connected to thefirst and/or the second electrodes and determining an amount of moisturewithin the insulation based on the measured complex impedance.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and characteristics of the present disclosure,as well as the methods of operation and functions of the relatedelements of structures and the combination of parts and economies ofmanufacture, will become more apparent upon consideration of thefollowing description and the appended claims with reference to theaccompanying drawings, all of which form a part of this specification,wherein like reference numerals designate corresponding parts in thevarious figures. It is to be expressly understood, however, that thedrawings are for the purpose of illustration and description only andare not intended as a definition of the limit of the invention.

Further features and other examples and advantages will become apparentfrom the following detailed description made with reference to thedrawings in which:

FIG. 1A is a perspective view of an insulated pipe including a coaxialmoisture sensor according to an embodiment of the present disclosure;

FIG. 1B is a cross-sectional view of the insulated pipe of FIG. 1A takenalong line 1B-1B;

FIG. 2A is a perspective view of another embodiment of an insulated pipeincluding a coaxial moisture sensor;

FIG. 2B is a cross sectional view of the insulated pipe of FIG. 2A takenalong line 2B-2B;

FIG. 3 is a perspective segmented view of a portion of a coaxialmoisture sensor according to an embodiment of the disclosure;

FIG. 4 is a perspective view of another embodiment of a moisture sensor;

FIG. 5 is a schematic drawing of electronic circuitry of a moisturesensor according to an embodiment of the disclosure;

FIG. 6 is a graph showing changes in complex impedance (ohms) as afunction of moisture content in wt. % for a dielectric materialaccording to an aspect of the disclosure;

FIG. 7A is a perspective view of an electronic device including moisturesensor(s) for detecting moisture ingression through the device housing,according to an embodiment of the disclosure;

FIG. 7B is a schematic drawing of the electronic device of FIG. 7A;

FIG. 8A is a perspective view of a storage tank including moisturesensor(s) for detecting moisture ingression into the tank and otherinformation according to an embodiment of the disclosure;

FIG. 8B is a cross sectional view of the storage tank of FIG. 8A takenalong line 8B-8B;

FIG. 9 is a flow chart of a process for monitoring liquids in a storagetank based on data from a moisture sensor, according to an embodiment ofthe disclosure;

FIG. 10A is top view of a coated panel including a moisture sensor,according to an embodiment of the disclosure;

FIG. 10B is a cross sectional view of the panel of FIG. 10A taken alongline 10B-10B; and

FIG. 11 is a schematic drawing of a vehicle and moisture detectingsystem including moisture sensors according to an embodiment of thedisclosure.

DETAILED DESCRIPTION OF THE INVENTION

For purposes of the following detailed description, it is to beunderstood that the invention may assume various alternative variationsand step sequences, except where expressly specified to the contrary.Moreover, other than in any operating examples, or where otherwiseindicated, all numbers expressing, for example, a duration of anelectric pulse or of a pause between pulses, as used in thespecification and claims are to be understood as being modified in allinstances by the term “about”. Accordingly, unless indicated to thecontrary, the numerical parameters set forth in the followingspecification and attached claims are approximations that may varydepending upon the desired properties to be obtained by the presentinvention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contain certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements.

Also, it should be understood that any numerical range recited herein isintended to include all sub-ranges subsumed therein. For example, arange of “1 to 10” is intended to include any and all sub-ranges betweenand including the recited minimum value of 1 and the recited maximumvalue of 10, that is, all sub-ranges beginning with a minimum valueequal to or greater than 1 and ending with a maximum value equal to orless than 10, and all sub-ranges in between, e.g., 1 to 6.3, or 5.5 to10, or 2.7 to 6.1.

As used herein, the singular form of “a”, “an”, and “the” include pluralreferents unless the context clearly dictates otherwise.

As used herein, the terms “right”, “left”, “top”, “bottom”, andderivatives thereof shall relate to the invention as it is oriented inthe drawing figures. However, it is to be understood that the inventioncan assume various alternative orientations and, accordingly, such termsare not to be considered as limiting. Also, it is to be understood thatthe invention can assume various alternative variations and stagesequences, except where expressly specified to the contrary. It is alsoto be understood that the specific devices and processes illustrated inthe attached drawings, and described in the following specification, areexamples. Hence, specific dimensions and other physical characteristicsrelated to the embodiments disclosed herein are not to be considered aslimiting.

As used herein, the terms “communication” and “communicate” refer to thereceipt or transfer of one or more signals, messages, commands, or othertype of data. “Electrical communication” refers to receipt or transferof power (e.g., current and/or voltage) between devices. For one unit orcomponent to be in communication with another unit or component meansthat the one unit or component is able to directly or indirectly receivedata or power from and/or transmit data or power to the other unit orcomponent. This can refer to a direct or indirect connection that can bewired and/or wireless in nature. Additionally, two units or componentscan be in communication with each other even though the data transmittedcan be modified, processed, routed, and the like, between the first andsecond unit or component. For example, a first unit can be incommunication with a second unit even though the first unit passivelyreceives data, and does not actively transmit data to the second unit.As another example, a first unit can be in communication with a secondunit if an intermediary unit processes data from one unit and transmitsprocessed data to the second unit. It will be appreciated that numerousother arrangements are also possible.

With reference to the figures, the present disclosure is generallydirected to structures, such as building fixtures, vehicles, electronicdevices, containers, and storage tanks enclosing, encapsulating, orincluding portions or areas which are intended to remain free from, orsubstantially free from, moisture and/or standing water. In some cases,moisture can damage these structures, as is the case with buildingfixtures (e.g., pipes and insulation) and vehicles. In other cases, themoisture could damage items contained within or enclosed by thestructure, as is the case for a storage container or housing for anelectrical device or appliance.

With specific reference to FIGS. 3-5, in order to identify, detect, orsense moisture and/or standing water in such structures, the structuresdisclosed herein include, are embedded with, and/or contain moisturesensors 100, 200 and associated electrical circuitry or sensorelectronics 310, such as a power source 312, voltmeter or similarelectrical measurement device 314, and controller 316. The moisturesensors 100, 200 and sensor electronics 310 are configured to detectmoisture or standing water in proximity to the sensors 100, 200. In someexamples, electrical signals from the moisture sensors 100, 200 may alsodetect a percentage of humidity in proximity to the moisture sensor 100,200. For example, humidity could be measured to monitor performance ofappliances intended to remain moisture-free, such as a paint booth orcure oven.

The moisture sensors 100, 200 disclosed herein include an absorbentmoisture reactive and/or moisture sensitive portion, such as a sleeve110 or layer 210, formed from a dielectric material. A dielectricmaterial or dielectric is an electrical insulator that can be polarizedby an applied electric field. When a dielectric is placed in an electricfield, electric charges do not flow through the material, as they do ina conductor. Instead, the electric charges only slightly shift fromtheir average equilibrium positions causing dielectric polarization.Because of dielectric polarization, positive charges are displacedtoward the field and negative charges shift in the opposite direction.This phenomena creates an internal electric field that reduces theoverall field within the dielectric itself. If a dielectric is composedof weakly bonded molecules, those molecules not only become polarized,but also reorient so that their symmetry axes align to the field.

The moisture sensors 100, 200 disclosed herein are configured tofunction as impedance moisture sensors, in which electrical impedance,i.e., the capacitance, resistance and complex impedance, of thedielectric material is monitored. Specifically, changes in electricalproperties of the dielectric material corresponds to an amount ofmoisture absorbed by the dielectric material and/or a humidity level inproximity to the dielectric material. It has been determined thatmoisture permeation into the dielectric material primarily causes anincrease in the capacitive component or complex impedance of thedielectric material of the moisture sensor 100, 200. In use, oncemoisture begins to enter into a structure or container, the absorbentmoisture sensitive layer absorbs moisture, which causes electricalproperties of the dielectric material to change. Specifically, compleximpedance of the dielectric material increases as moisture is absorbed.The change is identified and used to calculate the moisture level.

For purposes of clarity, impedance is the measurement of the oppositionto current flow in a circuit. For direct current (DC), the onlyopposition is the resistance of the circuit. For alternating current(AC), the current is opposed by the inductance and capacitance, as wellas by the resistance. The combination of inductance and capacitance isreferred to as reactance and makes up the complex component ofimpedance, while resistance forms the real component. Quantitatively,impedance is defined as the complex ratio of the voltage to the currentat a given frequency. For a sinusoidal input, the polar form of thecomplex impedance relates the amplitude and phase of the voltage andcurrent. The magnitude of the polar impedance is the voltage to currentamplitude ratio. The phase of the polar impedance is the phase shiftbetween the current and voltage.

According to another aspect of the disclosure, measurements from themoisture sensors 100, 200 can be used not only to determine aninstantaneous water ingression rate into a structure or container, butalso to record a history of the moisture ingression for the structureover a period of time. For example, impedance measurements from moisturesensors 100, 200 can be collected continually or periodically toidentify a rate of moisture ingression at particular intervals. Evidenceof moisture ingression over time may be used to identify times of daywhen moisture ingression commonly occurs or to determine if an amount ofstanding water in proximity to a moisture sensor increases or decreasesover time. Such moisture ingression information may be used to helpdetermine a cause of moisture entering the structure or container and/orto determine how to stop moisture from collecting in the structure orcontainer.

Insulated Pipes with Moisture Sensors

Referring to FIGS. 1A-2B, the structure being monitored may be aninsulated pipe 10 having at least one moisture sensor, such as thecoaxial moisture sensor 100, for monitoring moisture in proximity to thepipe 10. As described in greater detail in connection with FIG. 3, thecoaxial moisture sensor 100 is an impedance moisture sensor including adielectric member or sleeve 110 enclosed between an inner electrode 112,which can be a conductive wire, and a permeable annular outer electrode114. In some examples, the insulated pipe 10 could also include one ormore planar moisture sensors 200, such as the planar moisture sensorsshown in FIG. 4. The insulated pipe 10 includes an elongated tube 12having a first end 14, a second end 16, and a sidewall 18 extendingtherebetween. The elongated tube 12 can be formed from any suitablematerial commonly used in the building industry including, for example,metal (e.g., copper or galvanized steel), ceramic, or plastic, such as,polyvinyl chloride (PVC). In many configurations, the tube 12 includes ahollow cylindrical member with a cylindrical sidewall 18 and defining acylindrical cavity 20 extending axially therethrough. In other examples,the tube 12 and/or cavity 20 can have other cross sectional shapesincluding, but not limited to, a square, a rectangle, an oval, orcombinations thereof. For example, a pipe 10 having a square shapedcross section could define a circular cavity. Dimensions of the tube 12are largely dependent on intended use. For example, water supply pipesused for residential buildings may have an outer diameter OD of from 0.5inch to 1.5 inches. PVC pipes used for plumbing often have an outerdiameter from 0.75 inch to 3.0 inches.

The pipe 10 also includes an insulating member 22 at least partiallyenclosing a portion of the pipe sidewall. As shown in FIGS. 1A-2B, theinsulating member 22 is an elongated structure including a centralopening sized to receive the elongated tube 12, such that an innersurface 24 of the insulating member 22 is in contact with at least aportion of an outer surface 28 of the sidewall 18 of the elongated tube12. A radial thickness T of the insulating member 22 is selected basedon criteria including space considerations, material composition of theinsulating material, and typical or expected environmental conditionssurrounding the pipe 10. For example, pipes in interior walls of abuilding may only have a small amount of insulation. Pipes extendingthrough exterior walls often require thicker insulation. In most cases,the thickness T of the insulating member can be between 0.5 inch and 2.0inches. The insulating member 22 can be formed from any suitableinsulating material as is used in the building industry, including, forexample, fiber glass insulation, organic fiber materials (e.g., wool,cotton, or cellulose batts), spray foam materials (e.g., closed cellfoams, isocyanate foams), and similar materials. In one example, theinsulating member 22 is formed from FIBERGLAS™ pipe insulationmanufactured by Owens Corning Insulating Systems, LLC of Toledo, Ohio.In some examples, the insulating member 22 can be covered by an outerwrap or jacket (not shown) formed from a polymer film, fiberglass mat,or aluminum foil.

The insulating member 22 also includes one or more channels 30 extendingthrough at least a portion of the insulating member 22 sized to receivemoisture sensors 100, 200. For example, for a coaxial moisture sensor100 including an inner electrode formed on a wire 112 (shown in FIG. 3),the wire 112 can be positioned to extend through a channel 30 extendingaxially along a length L of the pipe 10. The channels 30 can be formedby any suitable method. For example, for spray foam insulation, foam maybe sprayed around the tube 12 and moisture sensor(s) 100 and allowed toharden, thereby forming channels 30. In other examples, channels 30could be cut or drilled into a surface or interior of insulatingmaterial and the moisture sensors 100, 200 could be fed through thechannels 30.

As will be appreciated by those of skill in the art, the channels 30 canbe positioned on or around the pipe 10 in a variety of configurationsand arrangements within the scope of the present disclosure. Positioningof the channels 30 is generally determined based on structuralproperties of the pipe 10, size of the pipe 10, and, for example, whattype of moisture is being detected. For example, as shown in FIGS.1A-2B, the channels 30 can be formed on the inner surface 24 of theinsulating member 22, so that the moisture sensors 100 are positionedbetween the tube 12 and the insulating member 22. In this position,moisture sensors 100 may be configured to detect when moisture has fullyabsorbed through the insulating member 22 and is nearly in contact withthe elongated tube 12, which could cause corrosion or other structuraldamage. Moisture sensors 100, 200 positioned on the outer surface 28 ofthe elongated tube 12 may also be used to detect leaks from the tube 12,which could damage or degrade the insulating member 22. In otherexamples, channels 30 could be formed extending through an interior ofthe insulating member 22 to detect moisture collecting in the insulatingmember 22. For example, a channel 30 may extend between inner and outersurfaces of the insulating member 22. In this position, information frommoisture sensors 100, 200 could be used to determine a moistureabsorption depth into the insulating member 22 or, for example, howclose moisture absorbed by the insulating member 22 is to contacting theelongated tube 12.

In one example, as shown in FIGS. 1A and 1B, the coaxial moisture sensor100 is wrapped around the elongated tube 12 in a helical arrangement.The dimensions of the helix, such as a step distance D, can be selectedbased on criteria including the length of the moisture sensor 100, 200,length of the pipe 10 or elongated tube 12, or, for example, selected tocover regions of the pipe 10 most likely to be exposed to moisture. Forexample, leaks may be most likely to occur at joints between separatesegments of the elongated tube 12. Accordingly, the moisture sensors 100may be concentrated near such joints. In some examples, the moisturesensor 100 is capable of sensing moisture along its entire length. Inthat case, a moisture sensitive layer, such as a dielectric sleeve 110,extends along an entire length of the inner electrode 112 or wire. Inother examples, separate dielectric sleeves 110 can be spaced apartalong a length of the inner electrode 112 or wire at random or discreteintervals, such as every 2 inches, 5 inches, or 10 inches. Measurementsfrom the separate dielectric sleeves 110 can be used to identify whichportions of the pipe 10 have been exposed to moisture.

In some examples, the insulated pipe 10 includes multiple coaxialmoisture sensors formed on different wires. For example, coaxialmoisture sensors 100 can be configured to form a double helix extendingaxially along the elongated tube 12, thereby increasing the surface areaof the pipe 10 and/or tube 12 being monitored for moisture. Dimensionsof the moisture sensors are not limiting for the invention; however, inorder to fit within the channels 30, the moisture sensor 100 can bemanufactured to be as thin as possible. For example, coaxial moisturesensors formed as described herein can be manufactured with a maximumouter diameter OD1 (shown in FIG. 3) of 0.060 inch or less.

With continued reference to FIG. 1A, the moisture sensor 100 isconnected to a control box 50 mounted to the outer surface 28 of thesidewall 18 of the elongated tube 12. As described in connection withFIG. 5, the control box 50 includes electronic circuitry configured toreceive electrical signals from the moisture sensor(s) 100 and processthe received signals to calculate a complex impedance of the moisturesensitive layer or dielectric sleeve 110, as described in greater detailherein.

As shown in FIGS. 2A and 2B, a pipe 10 may include a number ofsubstantially straight coaxial moisture sensors extending axially alongthe sidewall of the tube 12. For example, the insulated pipe 10 caninclude a first coaxial moisture sensor 100 a extending axially alongthe outer surface of the pipe at 12:00 (0 degrees), a second moisturesensor 100 b extending axially at 3:00 (90 degrees), a third moisturesensor 100 c at 6:00 (180 degrees), and a fourth moisture sensor 100 dat 9:00 (270 degrees). The pipe 10 also includes a control box 50electrically connected to the moisture sensor(s) 100 a, 100 b, 100 c,100 d. As described above, the control box 50 includes electricalcircuitry for receiving and processing electrical signals from themoisture sensors 100 a, 100 b, 100 c, 100 d.

Dielectric Moisture Sensors

With reference to FIG. 3, the coaxial moisture sensor 100 of the pipe 10includes the moisture sensitive layer, such as the dielectric sleeve 110defining a center hole 116, the inner electrode 112, and outer electrode114. The moisture sensor 100 may also include an outer protective layer122, such as an outer jacket or sleeve. The protective layer 122 can beformed from the same material as the dielectric sleeve 110. While theprotective layer 122 is not necessary to function of the sensor 100, theprotective layer 122 is believed to improve electrical efficiency andaccuracy of the sensor 100.

The dielectric sleeve 110 and other portions of the moisture sensor 100may be made from materials that are non-reactive with materials of otherportions of the pipe 10, such as the insulating member 22 and elongatedtube 12. The dielectric sleeve 110 can be formed from any insulatingmaterial having dielectric properties. The dielectric material may be anabsorbent polymer material, such as one or more of nylon of any chainlength (e.g., nylon 4-6, nylon 6, nylon 6-6, nylon 6-12, nylon 11),polyamide-imide, polybenzimidazole, polyethersulfone, or polysulfone.Since the coaxial moisture sensor 100 is formed over the inner electrode112 or wire, the dielectric material may be selected for compatibilitywith wire manufacturing and may have a large saturated moisture capacity(e.g., an equilibrium water absorption of 1.5% or more at ordinaryatmospheric conditions) and a melting temperature greater than alaminate processing temperature for other portions of the moisturesensor 100. For example, at ordinary atmospheric conditions (23° C./60%relative humidity) equilibrium water absorption is 3.5% for nylon 6,2.5% for nylon 6-6. The melting temperature of nylon 6 is about 215° C.and the melting temperature of nylon 6-6 is about 264° C.

The moisture sensor 100 further includes the opposing electrodes, suchas the outer electrode 114, which is electrically connected with anouter surface 118 of the dielectric sleeve 110, and the inner electrode112 or wire, which extends through the center hole 116 of and iselectrically connected with an inner surface 120 of the sleeve 110. Forexample, the outer electrode 114 can be in surface contact with theouter surface 118 of the dielectric sleeve 110 and the inner electrode112 can be in surface contact the inner surface 120 of the sleeve 110.

The inner electrode 112 and the outer electrode 114 may be formed froman electrically conductive material having a constant electricalconductivity over time at a fixed temperature. For example, theelectrodes 112, 114 can be formed from one or more of the noble metals(e.g., ruthenium, rhodium, palladium, silver, osmium, iridium, platinum,and gold) or non-noble metals and alloys such as, but not limited to,copper, tin-plated copper, nickel-plated copper, nickel-chromium,aluminum, and combinations thereof. Since the outer electrode 114surrounds the dielectric member or sleeve 110, the outer electrode 114may be at least partially porous, so that moisture or water passesthrough the outer electrode 114 and is absorbed by the dielectric memberor sleeve 110. For example, the outer electrode 114 can be a meshmaterial formed from woven metal fibers or filaments. The outerelectrode 114 can also comprise a carbon mesh or a flexible metal sheetcomprising holes or openings for permitting water to pass therethrough.

The dielectric member or sleeve 110 may be in electrical contact withthe inner and outer electrodes 112, 114 and maintains the inner and theouter electrodes 112, 114 spaced apart from one another. For example,the sleeve 110 maintain the inner and outer electrodes 112, 114 out ofsurface contact with one another. The inner electrode 112 and the outerelectrode 114 may be made of the same material to avoid chemicalreaction between two different metals. The moisture sensor 100 mayfurther comprises any number of additional moisture permeable conductingor insulating layers, which do not substantially change the electricalresponse of the moisture sensor 100, but may be useful for fabricationor installation of the sensor 110. For example, any additional moisturepermeable conducting or insulating layers should not affect the compleximpedance of the dielectric sleeve 110, should not create a separatepath between the electrodes 112, 114 for current to flow through havinga lower resistance than the sleeve 110, and should not reduce apotential of an electrical signal applied between the electrodes 112,114 through the dielectric sleeve 110.

In one specific example of the coaxial moisture sensor 100, the innerelectrode 112 is formed from a solid or stranded tin plated copper wire,such as a 44 American wire gauge (AWG) tin-plated copper wire with a 75%braid coverage, and the outer electrode 114 is made of a tin platedcopper mesh to provide passageways for moisture to move through theouter electrodes to contact the dielectric material.

In another specific example of the coaxial moisture sensor 100, theinner electrode 112 is formed from 28 AWG 7/36 tin-plated strandedcopper wire. The dielectric member or sleeve 110 is made of nylon-6purchased from Honeywell and sold under the trademark AEGIS® H55WC nylonjacket compound, which is extruded over the inner electrode 112 to anominal wall thickness of 0.005 inch. The outer electrode 114 is made of44 AWG tin plated copper braid, braided over the dielectric sleeve, witha nominal 75% coverage. An outer insulating layer or protective layer122 is formed from AEGIS® H55WC nylon jacket compound extruded over thebraid to a nominal outside diameter of 0.045 inch.

With reference to FIG. 4, an embodiment of a planar moisture sensor 200configured to detect changes in complex impedance of a moisturesensitive layer comprising a dielectric material is illustrated. Theplanar moisture sensor 200 comprises a first conductive electrode 212spaced apart from a second electrical conductive electrode 214. Theconductive electrodes 212, 214 are porous structures, such as perforatedmetal plates, meshes, carbon mesh, or similar structures as are known inthe art. The conductive electrodes 212, 214 can be formed from any ofthe noble and non-noble metal materials described above. As discussedpreviously, the electrodes 212, 214 are generally formed from the samemetal material to avoid chemical reactions between different metals. Theplanar moisture sensor 200 further comprises a dielectric layer 210positioned between and in physical contact, or close proximity, with thefirst electrode 212 and the second electrode 214. The dielectric layer210 can be an extruded film layer formed from an absorbent polymermaterial, such as one or more of nylon of any chain length (e.g., nylon4-6, nylon 6, nylon 6-6, nylon 6-12, nylon 11), polyamide-imide,polybenzimidazole, polyethersulfone, or polysulfone, as described above.

In a specific example of the planar moisture sensor 200, the moisturesensor 200 comprises a dielectric layer 210 formed from a layer ofnylon-6 dielectric material, ranging in thicknesses from 0.001 inch to0.032 inch, and having a width of 0.5 inch. A length of the dielectricmaterial can vary depending on a size of an area to be monitored by thesensor 200. In a specific example, the electrodes 212, 214 of the planarmoisture sensor 200 are made of nickel plated copper metalized polyesterfabric tape, with conductive pressure sensitive acrylic adhesive. Theelectrodes 212, 214 generally are the same length and width as thedielectric member or layer 210. The electrodes 212, 214 can have anominal thickness of 0.001 inch to 0.005 inch (0.025 mm to 0.13 mm) or0.002 inch to 0.004 inch (0.05 mm to 0.1 mm). The electrodes 212, 214can be from 0.25 inch to 0.5 inch wide. In some examples, the electrodes212, 214 of the planar moisture sensor 200 are joined to the top surface218 and the bottom surface 220 of the dielectric material by conductivepressure sensitive acrylic adhesive.

Moisture Sensor Electronics and Monitoring System

A schematic drawing showing a monitoring system 350 for analyzing andreporting such information to a user is provided in FIG. 5. The moisturemonitoring system 350 includes one or more moisture sensors, such as acoaxial moisture sensor 100, sensor electronics 310 configured toreceive and process electrical signals from the moisture sensor 100, andfeedback or data collection devices in wired or wireless communicationwith the sensor electronics 310. As described above, some components ofthe electrical circuitry or sensor electronics 310 can be contained in acontrol box, such as a control box 50 mounted to a portion of theinsulted pipe 10 (shown in FIGS. 1A-2B). Components of the monitoringsystem 350, such as a building monitor device, alarm systems, feedbackdevices, and similar electronic components, can be remote from and inwired or wireless electrical communication with the sensor electronics310 contained in the control box 50.

The sensor electronics 310 are configured to monitor, detect, oridentify changes in complex impedance of the dielectric material of themoisture sensor 100. The sensor electronics 310 can also be configuredto calculate moisture content of the dielectric material and/or amoisture content of structures surrounding the moisture sensor 100 basedon the measured complex impedance. In particular, as will be appreciatedby those skilled in the art, a measured general or complex impedance ofthe moisture sensor 100 can be calibrated to determine a moisturecontent of the moisture sensitive layer and to determine a moisturecontent of structures surrounding the sensor through a suitable modeland/or calibration curve. A non-limiting embodiment of a calibrationcurve, which can be used with the moisture sensor disclosed herein, isshown in FIG. 6.

With specific reference to FIG. 5, the sensor electronics 310 inelectrical communication with the moisture sensor 100 include a powersupply 312, such as an AC power supply, an electrical measurement device314, and a controller 316, such as a computer processor, configured toreceive an electrical signal from the moisture sensor 100 and calculatea complex impedance and moisture content based on the received signal.In some examples, the electrical power supply 312, the electricalmeasurement device 314, and the controller 316 are combined in a singleunit or instrument, e.g. a console of the type shown in FIG. 18A of, anddisclosed in U.S. Pat. No. 8,155,816. In other examples, the powersupply 312, measurement device 314, and controller 316 are separatedunits in wired or wireless communication with one another and with themoisture sensor 100.

The sensor electronics 310 also include elements for operativelyconnecting the electrodes 112, 114 of the moisture sensor 100 to thecontrol box 50 and sensor electronics 310. For example, the innerelectrode 112 of the moisture sensor 100 can be connected to a pole 322of the power supply 312 through a wire or lead 324. The outer electrode114 can be connected to a second pole 326 of the power supply 312 by asecond wire or lead 328 to apply a voltage to the moisture sensor 100.This connection allows the moisture sensor 100 to act as an electricalcircuit in which the electrical power supply 312 applies an electricalpotential to the moisture sensor 310 through the leads 324, 328.

The power supply 312 can be any conventional electrical source, such as,but not limited to, a battery, an electrical generator, and the like forapplying a voltage to the moisture sensor 310. The power supply 312 canbe configured to apply alternating electrical current to the inner andouter electrodes according to a pattern or protocol, which can bedirected by the controller 316.

The electrical measurement device 314 is configured to measure compleximpedance (ohms) of the moisture sensor 310 based on an electricalsignal received from the inner and outer electrodes 112, 114. Forexample, the electrical measurement device can be an ammeter orvoltmeter operatively connected to the electrodes 112, 114. In otherexamples, complex impedance (ohm) output of the moisture sensor 100 canbe measured using a variety of standard readout sensor circuits, e.g. ofthe type disclosed in U.S. Pat. No. 9,347,905.

The controller 316 can be any type of electronic or computerized devicewith sufficient processing capacity to analyze information provided bythe electrical measurement device 314. For example, the controller 316can be a dedicated electronic device installed in the control box 50.The controller 316 can also be a computer device with software forreceiving and processing information from the electrical measurementdevice 314. The controller 316 can measure complex impedance from thesensor 310 by causing the power source 312 to provide a predetermined orspecifically set electrical potential to the electrodes 112, 114 of themoisture sensor 100 and measuring a response from the moisture sensor100 with the measurement device 314. The controller 316 can collectand/or calculate the electrical potential of the moisture sensor 100 viathe electrical measurement device 314 to calculate complex impedanceand/or moisture content of the dielectric material of the sensor 100.

An impedance measurement for the coaxial moisture sensor 100 can beperformed by the following process. This process can also be used tocalculate complex impedance for the planar moisture sensor 200, shown inFIG. 4. First, moisture penetrates through the insulation material ofthe pipe, eventually reaching and being absorbed by the dielectricmaterial or sleeve 110 of the moisture sensor 100. An amount of moistureabsorbed by the dielectric sleeve 110 is calculated based on thepredictable increase in complex impedance (ohms) resulting from theabsorbed moisture. In order to measure complex impedance, voltage isapplied to the electrodes 112, 114 and the impedance of the circuitmeasured. As the dielectric material or sleeve 110 continues to absorbmoisture, the dielectric material becomes saturated with moisture and nolonger significantly absorbs moisture. The absolute moisture content ofthe dielectric material depends on the thickness and absorptioncoefficient of the dielectric material. The absolute moisture content ofthe dielectric material may also be temperature dependent. Accordingly,a calibration curve or model for moisture content of the sensor may be atemperature dependent model.

The impedance measurement may be made by analyzing a phase shift of aknown frequency applied to the moisture sensor 100. In that case, theelectrical power supply 312 applies an AC voltage to the moisture sensor100, as set or specified by the controller 316. This applied voltageresults in a measured potential on the sensor 100, which can be measuredby the electrical measurement device 314. Importantly, the measuredposition is different in phase and magnitude from the voltage applied bythe power supply 312. Since the electrical power supply 312 applies aset voltage and the electrical measurement device 314 reads or measuresa voltage difference from the moisture sensor 100, the electricalmeasurement device 312 and/or the controller 316 are capable ofcalculating the complex impedance (ohms). Specifically, the compleximpedance is calculated based on a voltage magnitude and a phasedifference between the inner electrode 112 and outer electrode 114 ofthe moisture sensor 100. The complex impedance is then used to indicatethe amount of moisture absorbed by the dielectric material or sleeve 110of the moisture sensor 100. The electrical signal frequency used forthis measurement is typically chosen to maximize the response of thesensing element to moisture change, however multiple frequencies can beused to improve accuracy and reduce the impact of noise.

In another example, the impedance measurement is made by applying a DCvoltage across the electrodes 112, 114 and the charge time is measured(time it takes for the sensing element to reach the applied DC voltage).The electrical power supply 312 applies the DC voltage to the moisturesensor 100, again as set or specified by controller 316. This appliedvoltage results in a measured potential difference (as measured by theelectrical measurement device 314) on sensor 100 that approaches theapplied voltage. The electrical measurement device 314 or the controller316 is able to calculate the capacitance (farads) of the moisture sensor100 based on a time to reach the applied voltage. The capacitance of thesensor 100 is then used to indicate the amount of moisture absorbed bythe dielectric material or sleeve 110 of the moisture sensor 100. Inorder to obtain continuous measurements, a changing DC voltage can beused, as well as measurement of both charge and/or discharge times.

Once complex impedance is calculated, the controller 316 is configuredto determine an amount of moisture absorbed by the moisture sensitivelayer or dielectric sleeve 110 based on the measured complex impedance.As described above, a graph or calibration curve comprising a measuredcomplex impedance is illustrated. As shown in FIG. 6, the “y”, orvertical axis, is the imaginary component of the complex impedance(ohms) and the “x”, or horizontal axis, is the moisture content of astructure, such as the insulation member, which surrounds the moisturesensor 100. More specifically, the graph shown in FIG. 6 is a model(solid curve) with one set of recorded data for the complex impedance(ohms) of the sensor 100.

The monitoring system 350 also includes components which analyze datafrom the moisture sensors 100 and controller 316 and provide theinformation to a user. For example, information about moisture level ortrends over time can be analyzed to identify when moisture levelsincrease or when leaks are mostly likely to occur. Such information canbe displayed to a user on a remote computer device 352, such as apersonal computer, tablet, smart phone, or similar device in wired orwireless communication with the controller 316 and moisture sensor 100.For example, the controller 316 can be coupled to a wired or wirelesstransmitter 330 for sending data from the controller 316 to a remotecomputer device 352 of the monitoring system 350.

The controller 316 and wireless transmitter 330 may be configured tosend periodic updates or reports about measured moisture or compleximpedance to the remote device 352. In that case, the monitoring system350 can include computer memory, such as a database 354, for storingreceived information from the moisture sensor 100 and/or controller 316.For example, the database 354 may store moisture or complex impedancevalues over time to create a historical record documenting moistureingress into a structure or container.

The computer device 352 can also display or provide real time alerts ornotifications about elevated moisture levels to the user. In order togenerate such alerts, the controller 316 can be configured to compare ameasured complex impedance or moisture level measured by the moisturesensor 100 to a predetermined threshold value. The predeterminedthreshold value could correspond, for example, to an amount of moisturethat the insulating member can absorb before damage to the insulatedpipe or insulating material begins to occur. When the controller 316determines that the measured moisture value exceeds the predeterminedthreshold value, an alert is generated to inform the user about theincreased moisture. The alert or notification can be wirelesslytransmitted from the controller 316 to the remote computer device 352.The remote computer device 352 can be configured to provide visualand/or audio indications to the user informing the user about theincreased moisture levels.

In some examples, the remote device 352 can be configured to receiveinformation from a plurality of moisture sensors 100 located atdifferent positions on a structure or container being monitored. Thecontroller 316 could also receive information from other moisturesensors or other types of sensors located on different structures ordevices. By receiving and analyzing moisture measurements from differentlocations, it is possible to determine which areas of a structure orcontainer receive the most moisture and/or are mostly likely to bedamaged by moisture. Considering information from multiple sensors 100also allows the user to evaluate whether certain sensors are functioningproperly. For example, if different sensors located in similar areas ofa structure or container detect different complex impedance or moisturevalues, it may indicate that a sensor is malfunctioning and should berepaired or replaced.

In a similar example, the computer device 352 could be a building-widemonitoring system that receives moisture measurements from moisturesensors positioned on different electrical devices, appliances, and/orbuilding fixtures located throughout the building. The received moisturesensor information could be used to evaluate which building systems arefunctioning normally. In a similar manner, moisture measurements fromdifferent sensors could be compared to determine a source of moisture orto identify leaks that only affect some floors or areas of the building.In a similar manner, the computer device 352 could be a computer controlsystem for a vehicle, such as an airplane or automobile. In that case,moisture measurements from different locations on the vehicle could beused to evaluate performance of different vehicle systems, determinewhich vehicle systems are functioning in an expected manner, and/or toschedule maintenance activities for different vehicle systems.

Electronic Housing Including Moisture Sensors

According to another aspect of the disclosure, the coaxial moisturesensor 100 and monitoring system 350 disclosed herein can be used tomonitor structural integrity of a housing or container and, inparticular, to identify moisture ingression through the housing orcontainer, which could damage goods or devices stored therein. Forexample, the container or housing could be a housing of an electronicdevice 400, such as a small appliance or portable electronic device(e.g., a tablet computer, cell phone, smartphone, personal digitalassistant (PDA), calculator, or similar device), as shown in FIGS. 7Aand 7B. In that case, the moisture sensor 100 could be configured todetect moisture ingress through the housing or container, which coulddamage electrical components contained therein.

In other examples, the container could be a container for perishablegoods, such as food items, which would be damaged or destroyed whenexposed to moisture. In that case, information about moisture ingressthrough the container may be used to determine when a container needs tobe repaired or replaced, or when food items in the container havespoiled and should be discarded. In other examples, as described ingreater detail in connection with FIGS. 8A, 8B, and 9, the containercould be a liquid storage tank, such as a fuel storage tank. In thatcase, measurements from moisture sensors 100 could detect leaks from thetank, moisture ingress into the tank, a volume of liquid in the tank,and/or a concentration of liquids in the tank.

An exemplary electronic device 400 comprising coaxial moisture sensors100 a, 100 b configured to identify moisture ingress into the device 400is shown in FIGS. 7A and 7B. Moisture sensors 100 a, 100 b can be theimpedance moisture sensors 100 formed on an inner electrode 114 or wire,as shown in FIG. 3. The electronic device 400 includes a housing 410comprising a top 412, a bottom 414, and sides 416 extendingtherebetween. The housing 410 encloses an interior volume or cavity 418and prevents moisture ingression into the cavity 418. As such, thehousing 410 is generally formed from a non-porous material, such asmetal, plastic, or glass. In some examples, the housing 410 is anintegral structure, such as a plastic structure formed by a moldingprocess. In other examples, the housing 410 is formed from varioussegments or portions connected together to form the housing 410. In thatcase, joints between the segments or portions of the housing 410 mayinclude adhesives, solder, or sealing materials to reinforce the jointsand to prevent moisture from leaking into the housing 410 through thejoints. The housing 410 could also include an opening or port covered bya removable cap or cover to allow a user to access the cavity 418 to,for example, manipulate electronic components contained in the cavity418. In that case, the cover or port could include a seal to preventmoisture ingression between the cover and port.

As shown in FIG. 7B, the electronic device 400 also includes electroniccomponents stored in the cavity 418. For example, the device 400 caninclude a processor or controller, such as a CPU 422, operativelyconnected to computer memory 424, and a wireless transmitter 428. Theelectronic device 400 can also include various other electroniccomponents including, in the case of consumer appliances, motors,heating elements, and associated controllers. For portable electronicdevices such as smart phones, the electronic device 400 can also includea visual display, a cellular transceiver, speakers, microphones, andsimilar components, as are known in the art. The electronic device 400can also include power supply components, such as batteries 426, forproviding power to the CPU 422 and other components.

As shown in FIGS. 7A and 7B, moisture sensors 100 a are positioned inthe cavity 418 and are configured to detect moisture ingress throughportions of the housing 410. The moisture sensors 100 a can be arrangedin a variety of patterns based, for example, on which areas of thehousing 410 are most likely to be exposed to moisture and/or which areasof the housing are most likely to leak. For example, moisture sensors100 a may be positioned near joints, corners, between adjacent segmentsor walls of the container 410, or near covered openings (e.g., a coverof a battery port of an electronic device), since moisture often entersthe housing 410 through such areas or openings. As shown in FIGS. 7A and7B, moisture sensors 100 a are positioned around peripheral portions ofthe top 412 and sides 416 of the housing 410 for detecting moistureingression between portions of the sides 416 and/or between the sides416 and top 412 or bottom 414 of the housing 410.

Other moisture sensors can be positioned in the cavity 418 in proximityto important electrical components of the electronic device 400. Forexample, as shown in FIG. 7B, moisture sensors 100 b are positioned nearthe CPU 422, computer memory 424, and batteries 426.

The electronic device 400 can also include a control box 450 containingelectrical circuitry or sensor electronics for receiving and processinginformation from the moisture sensors 100 a, 100 b positioned indifferent portions of the cavity 418. As in previous examples, thecontrol box 450 can enclose a power supply, electronic measurementdevice, and controller (shown in FIG. 5) in electronic communicationwith the moisture sensors 100 a, 100 b. The control box 450 can beprovided in any convenient location in proximity to other portions ofthe housing 410. For example, as shown in FIG. 7B, the control box 450is placed in the cavity 418 near the interior surface 420 of the top 412of the housing 410. In other examples, the control box 450 could bemounted to a side 416 or top 412 of the housing 410. In other examples,the control box 450 could be remote from the container and in wired orwireless communication with the one or more moisture sensors 100 a, 100b through suitable data transmission components, as are known in theart.

The moisture sensors 100 a, 100 b are configured to detect moistureingression through the housing 410. Specifically, electrical signalsfrom the moisture sensors 100 a, 100 b are processed by sensorelectronics in the control box 450 to measure a complex impedance and/ordetect moisture based on information sensed by the moisture sensors 100a, 100 b. In some examples, the sensor electronics in the control box450 can transmit warnings or notifications to remote devices whenmoisture is detected. In some examples, sensor electronics in thecontrol box 450 can also communicate with the electronics, such as theCPU 422, of the electronic device 400 when moisture is detected. Forexample, in order to avoid or reduce damage caused from moistureingression through the housing 410, the controller 316 (shown in FIG. 5)of the moisture sensors 100 a, 100 b can be configured to transmit asignal to the CPU 422. In response to the signal from the controller316, the CPU 422 can be configured to perform actions to protectcomponents of the electronic device 400 including causing electricalcomponents of the device 400 to turn off or power down, causing thecomputer memory 424 to perform a save function to preserve data, orcausing the wireless transmitter 428 to transmit data from the device400 to a remote source, so that it can be stored safely in the eventthat moisture damages the device 400. After a period of time, if themoisture sensor 100 detects that moisture level has dropped and that itis safe to continue operating the electronic device 400, the controller316 of the moisture sensor 100 could provide an instruction to the CPU422 of the electronic device 400 instructing the device 400 to resumenormal operation.

Storage Tank with Moisture Sensors

According to another aspect of the disclosure, one or more coaxialmoisture sensors 100 a, 100 b, 100 c can be mounted to a liquid storagetank 500, such as a storage tank for storing liquid fuels, such aspetroleum, gasoline, diesel, liquid propane, kerosene, and liquefiednatural gas. In some examples, coaxial moisture sensor can be configuredto monitor a volume of liquid in the tank 500. In other examples,moisture sensor(s) could be arranged to detect leaks from and/ormoisture ingress into the tank 500. In other examples, measurements fromthe moisture sensors could be used to detect a concentration of polarand non-polar fluids in the tank. For example, measurements frommoisture sensors could be used to detect a concentration of oil andwater in a storage tank 500.

With reference to FIGS. 8A and 8B, the storage tank 500 can comprise abody 510 having a top 512, a bottom 514, and sides 516 extendingtherebetween. The body 510 encloses an interior volume 520 or storagecapacity for a liquid contained in the tank 500. The tank 500 can have awide range of volumes based on the intended use and type of liquid beingstored. For example, a free-standing fuel tank may have a volume of from50 gallons to 100 gallons or more. The body 510 can be formed from anysuitable non-porous material which is inert and/or non-reactive with theliquids stored in the tank 500. For example, for a fuel tank, the tankbody 510 can be formed from a coated metal material, such as aluminum orsteel, coated with a protective coating, such as a polyurethane coating,to prevent leaks through the body 510 and/or to prevent portions of thebody 510 from corroding due to prolonged exposure to moisture. In someexamples, the storage tank 500 is an enclosed structure including, forexample, a removable cap 518 configured to seal an opening 524 of thetank 500 to create a fluid-tight sealed structure. In other examples,the tank 500 can include a fluid port and valve configured to receive anozzle for delivering fluid to and/or extracting fluid from the tank500. In other examples, the tank 500 can be connected to a network offluid delivery pipes or conduits which deliver fluid to and extractfluid from the storage tank 500.

As in previously described examples, the moisture sensors 100 a, 100 b,100 c can be a coaxial moisture sensor formed on a wire, such as theinner electrode 112 shown in FIG. 3. The coaxial moisture sensors 100 a,100 b, 100 c are configured to be mounted to a portion of the body 510,the location of which is determined based on types of moisture beingdetected. For example, as shown in FIGS. 8A and 8B, a coaxial moisturesensor 100 a can be positioned on an outer surface 526 of the body 510to detect leaks from the tank 500. In some examples, as shown in FIG.8A, the coaxial moisture sensor 100 a could be positioned to extendacross an outer surface of the tank body 510 in an undulating orsinusoidal pattern, which increases the surface area of the tank 500that can be monitored by a single sensor 100 a. The moisture sensor 100a can also be arranged in other patterns including, for example,extending around the storage tank in a helical or spiral pattern,extending axially along the tank 500 in a straight line, or extendingaround peripheral portions of sides of the tank 500. The moisture sensor100 a can be mounted to an outside surface of the tank 500, so that amoisture or humidity of surrounding air or soil can be measured. Inother examples, as shown in FIG. 8B, the moisture sensor 100 a can beenclosed by a coating 528 or insulating material and configured toidentify both leaks from the tank 500 and moisture ingress through theinsulation or coating 528.

With reference to FIG. 8B, the storage tank 500 can further include oneor more moisture sensor(s) 100 b positioned in the interior volume 520of the storage tank 500. For example, moisture sensor(s) 100 b can bemounted to a portion of an inner surface 522 of the storage tank 500.Some of the moisture sensors 100 b can be positioned to measure a levelof liquid or fluid F or a volume of fluid F in the tank 500. Forexample, moisture sensor(s) 100 b could be positioned randomly or atdiscrete distances or depths from the top surface 512 of the tank 500,such as every 2 inches to 4 inches. Measurements from the moisturesensor(s) 100 b could detect which sensors 100 are submerged by thefluid F contained in the tank 500 and which sensors 100 b are notsubmerged. Based on this information, the fluid level and fluid volumefor fluid F could be calculated.

Moisture sensors 100 in the tank 500 may also be used to determineinformation about a composition of fluid F contained in the tank 500.For example, impedance measurements from moisture sensor(s) 100 c couldbe used to determine or estimate a concentration of polar and non-polarfluids F. More specifically, the moisture sensors 100 c are impedancemoisture sensors including the absorbent dielectric material, which isaffected by a polarity of liquids absorbed by the material. As such,complex impedance measurements from the moisture sensor 100 c can becorrelated to a concentration or amount of polar liquid absorbed by thesensors 100 c. For example, complex impedance measurements from themoisture sensor 100 c can distinguish between a non-polar liquid, suchas oil or gasoline, and a polar liquid, such as water. In most cases, asensor 100 c for identifying a concentration of liquid in the tank 500is positioned near the bottom 514 of the storage tank 500, so that itwill be covered with fluid F in most circumstances. For example, acoaxial moisture sensor 100 c could be mounted to the inner surface 522of a bottom 514 of the tank 500. In other examples, the moisture sensor100 c could be positioned on interior surfaces of sides 516 of the tankor other convenient locations. In some examples, moisture sensors 100 cfor sensing a concentration of liquid could also be positioned at aninflow or outflow port or opening, such as opening 524, to measureconcentration of liquids enter or exiting the tank 500.

A flow chart illustrating a process for monitoring fluid contents of astorage tank 500 based on information sensed or detected by a moisturesensor(s) is shown in FIG. 9. The moisture sensor(s) can be one or moreof the coaxial or planar moisture sensors 100, 200 described herein. Themoisture sensors 100, 200 include a dielectric moisture sensitive layeror sheet and are configured to detect, monitor, or identify changes incomplex impedance of the moisture sensitive material.

As shown in box 910, a power supply operatively connected to themoisture sensor continually or periodically applies an alternatingelectrical current to the moisture sensor positioned on a portion of astorage tank. As shown at box 912, an electric measurement devicemeasures an electric potential of a signal received from the moisturesensor in response to the applied current. As shown at box 914, sensorelectronics, such as a controller or processor, determine a compleximpedance for the moisture sensor based on a comparison of the appliedcurrent and measured response. As shown at box 916, an amount ofmoisture present in proximity to the moisture sensor can be calculatedbased on the complex impedance.

The controller or processor can determine characteristics of the storagetank and liquids contained therein based on the measured compleximpedance. For example, for sensors located on an outer surface of thetank for detecting leaks and/or for sensors inside the tank fordetecting moisture ingression into the tank, the detected moistureamount can be compared to a target value for a maximum acceptable amountof moisture, as shown at box 918. When the moisture amount measured bythe moisture sensor exceeds the target value, as shown at box 920, thesensor electronics may provide an alert, notification, or warningindicating that leaks into or from the tank have been detected.

For moisture sensors configured to detect a level of fluid in a tank,the sensor electronics can receive moisture information from sensorslocated at different depths in the tank. Responses from the differentsensors can be used to determine which sensors are submerged in liquidand which sensors are not submerged. Based on this determination, asshown at box 922, the controller determines or estimates a volume ofliquid in the storage tank and provides the determined or estimatedliquid volume to a user.

As shown at box 924, for moisture sensors configured to determine aconcentration of polar and non-polar liquids in the tank, a compleximpedance measurement for a submerged sensor can be received by thecontroller. The controller can determine a concentration of polar andnon-polar liquids in the storage tank based on a correlation between ameasured complex impedance and liquid concentration. For example, thecorrelation can be based on an experimentally derived model comparingcomplex impedance for a moisture sensor submerged in a liquid and aconcentration of polar and non-polar portions of the liquid. Thecontroller can also cause the determined or estimated concentrationvalue to be provided to the user.

Once information about the storage tank and liquids contained therein isdetermined, as shown at box 926, the controller can also be configuredto transmit detected and calculated information to a remote source, suchas a computer device or computer network. For example, information aboutliquids contained in the tank could be periodically transmitted to adatabase for recording information about the storage tank and liquidscontained therein over time. Information about the tank condition overtime could be analyzed to determine, for example, when to schedulerepairs and/or to estimate a remaining useful life for the storage tank.In a similar manner, information about a concentration of polar andnon-polar liquids over time may be used to determine a shelf life orstorage life for fuel in the tank.

Moisture Sensors for Vehicles

According to another aspect of the disclosure, a moisture sensor, suchas the coaxial moisture sensor 100, shown in FIG. 3, or the planarmoisture sensor 200, shown in FIG. 4, could be configured to identifymoisture ingression into areas of a vehicle (e.g., a land, sea, or airvehicle) which are intended to remain free from, or substantially freefrom, moisture. For example, a moisture sensor could be positioned in ornear a portion of a vehicle which is difficult for technicians ormechanics to access to provide an indication about a status or conditionof the inaccessible portion of the vehicle. Moisture sensors 100 couldalso be positioned on or embedded in coated panels of such vehicles toprovide information about moisture ingression through the coating, whichcould be used to determine when a coating has failed and/or when a panelof a vehicle needs to be replaced.

With specific reference to FIGS. 10A and 10B, in one example, coaxialmoisture sensors 100 a, 100 b are provided on a panel 600, such a panelhaving an opposing top surface 612 and a bottom surface 614. As shown inFIGS. 10A and 10B, the panel 600 is a substantially flat panel. However,the moisture sensors 100 a, 100 b disclosed herein can also be used withcurved panels, angled or inclined panels, or panels having adiscontinuous surface. In some instances, the panels may also bebendable or deformable, such that the panels have a flat surface in someenvironmental conditions and a curved surface in other environmentalconditions. As in previous examples, the coaxial moisture sensors 100 a,100 b are formed on an inner electrode 112 (shown in FIG. 3) or wire andextend across a surface of the panel 600. The panel 600 can be formedfrom any rigid structural material, as is used in the manufacture ofvehicles, including metals, plastics, ceramics, and/or glass. Themoisture sensors 100 a, 100 b can be positioned to monitor moisture atvarious portions of the top and/or bottom surfaces 612, 614 of the panel600. For example, the panel 600 includes a moisture sensor 100 aextending across a central portion 616 of the panel 600, such as in asinusoidal pattern, as shown in FIG. 10A. The panel 600 also includes amoisture sensor 100 b positioned along a periphery 618 of the panel 600to hide the sensor 100 b from view and/or for other aesthetic purposes.Moisture sensors 100 positioned near the periphery 618 of panels 600 mayalso be configured to detect moisture ingression through joints orspaces between adjacent panels 600 of a vehicle, which could causedamage to an interior of the vehicle.

At least a portion of the surface(s) 612, 614 of the panel 600 andmoisture sensor 100 can be covered with one or more coating layers 620.For example, the panel 600 can be coated with a moisture resistant layer620 configured to protect the panel 600 from moisture and corrosion.Layers formed from other coating materials, as are known in the art,such as coatings which reflect solar radiation, scratch resistantlayers, heat reflective layers, and/or aesthetic layers (e.g., layersincluding paints or pigments) can also be applied within the scope ofthe present disclosure. As shown in FIGS. 10A and 10B, the coatinglayer(s) 620 extend over the top surface 612 of the panel 600 andenclose or partially enclose portions of the moisture sensors 100 a, 100b. For example, during manufacture of the panel 600, the moisturesensors 100 a, 100 b could be attached to the top surface 612 of thepanel 600 in a desired pattern or arrangement with an adhesive, such asa pressure sensitive acrylic adhesive. Once the moisture sensors 100 a,100 b are in place, a layer of moisture resistant material could besprayed or otherwise deposited across the top surface 612, enclosingboth the top surface 612 and the moisture sensors 100 a, 100 b. Moisturemeasurements from the enclosed moisture sensors 100 a, 100 b could thenbe used to identify moisture ingression through the coating layer(s) 620which could damage other portions of the panel 600.

With specific reference to FIG. 10A, the panel 600 and moisture sensor100 can further include a control box 650 containing sensor electronicsmounted to the panel 600 or to another portion of a vehicle. Forexample, a wire or lead 622 can extend from electrodes of the moisturesensors 100 a, 100 b, through a peripheral portion of the coating layer620, and to the control box 650. As in previously described examples,the control box 650 contains sensor electronics for providing anelectrical signal to the moisture sensors 100, receiving a responsesignal from the sensors 100, and determining complex impedance based onthe received signal. In some examples, the control box 650 is connectedto a single moisture sensor 100. In other examples, multiple moisturesensors 100, such as sensors 100 located on different panels 600 of avehicle and/or monitoring different portions of the vehicle, can beelectrically connected to a signal control box 650. In that case, thecontrol box 650 can monitor complex impedance at different portions of apanel 600 and/or vehicle to provide information about moisture ingressor standing water at different positions along the panel 600 and/orvehicle.

As described above, the panels 600 and moisture sensors 100 a, 100 bdisclosed herein can be portions of a vehicle. For example, one or morepanels 600 could be joined together to form a body of the vehicle. Thevehicle can be any land, water, or air vehicle as is known in the artincluding, for example, automobiles, trucks, all-terrain vehicles(ATVs), airplanes, helicopters, drones (e.g., remotely controlled flyingdevices), ships, and submarines. A vehicle can include multiple moisturesensors positioned on different panels of the vehicle to monitor acondition of panels and coatings at different positions along thevehicle surface. The vehicle can also include moisture sensorspositioned at other hard to reach portions of the vehicle to detectmoisture, standing water, or otherwise monitor a condition of thevehicle. For example, moisture sensors could be positioned on anundercarriage of an automobile to identify whether standing water ispresent which could cause corrosion. In a similar example, moisturesensors could be provided on drones and configured to transmit moisturemeasurements to remote locations while the drone is in flight. Forexample, moisture measurements could be shown to a drone pilot to helpthe pilot monitor a condition of the drone during flight and to identifywhen moisture is present, which may damage the drone. Similar moisturesensing systems could be provided on hulls of ships, airplane fuselagesand similar structures for providing information about moisture ingressand/or areas of standing moisture.

With reference to FIG. 11, a moisture monitoring system 700 for avehicle 750 is illustrated. The vehicle 750 shown in FIG. 11 is anautomobile, though it is understood that similar monitoring systemscould be used with many other types of vehicles. The monitoring system700 includes a plurality of moisture sensors, such as coaxial moisturesensors 100 and/or planar moisture sensors 200, positioned at differentlocations on the vehicle 750. For example, the vehicle 750 can includepanels, such as door panels 752, front body panels 754, and rear bodypanels 756. The panels 752, 754, 756 can be the coated panels 600 shownin FIGS. 10A and 10B and can include one or more coaxial moisturesensors 100 for detecting moisture ingression through the panels 752,754, 756. The vehicle 750 can also include one or more moisture sensors100 positioned in areas which should remain free from or substantiallyfree from moisture to avoid damaging the vehicle 750. For example, itmay be acceptable for small amounts of moisture to collect in suchareas. However, a volume of the moisture should be small, shouldevaporate quickly, and should not be permitted to remain in such areasfor any longer than a few minutes or hours. In that case, the sensors100 could be configured to detect standing water and to monitor how longthe standing water is present. The system could be configured to providean alert when detected standing water is present for longer than apredetermined period of time. Such moisture sensors 100 can bepositioned in a trunk 758 of the vehicle 750 for detecting whethermoisture leaks into and/or collects in portions of the trunk 758. Othermoisture sensors 100 could be positioned near seals surrounding windows760 and windshields 762, as moisture may enter an interior of thevehicle through window openings. The vehicle 750 can also includemoisture sensors 100 positioned near portions of a vehicle power trainto detect moisture ingression to an engine block, transmission, or driveshaft of the vehicle 750.

As shown schematically in FIG. 11, the moisture sensors 100 areelectrically connected to a vehicle computer system 710. The vehiclecomputer system 710 includes sensor electronics 712 for the sensors 100and can include, for example, a power supply for applying alternatingcurrent to the sensors 100, an electronic measurement device, and one ormore controllers for receiving and processing information from thesensors. The system 710 can also include a moisture detection module 714for receiving information from the sensor electronics 712, analyzing thereceived information, and drawing conclusions about a status of portionsof the vehicle 750. For example, the moisture detection module 714 couldconsider which moisture sensors 100 of the vehicle 750 detect moistureand which do not. Based on such a consideration, the moisture detectionmodule 714 could determine whether the vehicle is safe to operate,whether maintenance is required, or whether one or more of the sensorsmay be malfunctioning or providing incorrect readings. The moisturedetection module 714 could also be configured to emit warnings,notifications, or alerts based on the determined status of the vehicleand/or detected moisture. The vehicle computer system 710 can alsoinclude a user feedback or user interface module 716 configured toreceive alerts, warnings, and notifications from the moisture detectionmodule 714 and provide them to a user, such as a driver. In someexamples, alerts, warnings, or notifications could also be stored onsystem memory 718, so that they can be reviewed by a technician ormechanic at a later date.

In view of the foregoing description and Examples, the present inventionthus relates inter alia to the subject matter of the following clausesthough being not limited thereto.

Clause 1: An insulated pipe comprising: an elongated tube comprising afirst end, a second end, and a sidewall extending therebetween; aninsulating member at least partially enclosing a portion of the pipesidewall, the insulating member comprising at least one channelextending through at least a portion of the insulating member; and atleast one coaxial moisture sensor positioned within at least a portionof the channel configured to sense moisture in the channel, the at leastone coaxial moisture sensor comprising: a dielectric member comprising asleeve defining a center hole formed from an absorbent dielectricpolymer material; an outer electrode electrically connected with anouter surface of the dielectric member, the outer electrode comprising amoisture permeable sleeve which permits moisture to pass to thedielectric member; and an inner electrode comprising a wire extendingthrough the center hole of and electrically connected with an innersurface of the dielectric member, wherein the dielectric member is inelectrical contact with the first and second electrodes and maintainsthe first and the second electrodes spaced from one another.

Clause 2: The insulated pipe of clause 1, further comprising sensorelectronics operatively connected to the electrodes of the moisturesensor to measure an electrical property of the moisture sensor todetermine an amount of moisture absorbed by the dielectric member,wherein the sensor electronics comprise: a power source for applyingalternating electrical current to at least one of the first electrodeand the second electrode; and an electrical measurement deviceconfigured to measure a complex impedance (ohms) of the dielectricmember.

Clause 3: The insulated pipe of clause 2, wherein the sensor electronicsfurther comprise a controller operatively connected to the power sourceand to the electrical measurement device, and wherein the controller isconfigured to cause the power source to periodically apply thealternating current to at least one of the electrodes.

Clause 4: The insulated pipe of clause 3, wherein the controller isfurther configured to determine an amount of moisture within the channelbased on the measured complex impedance.

Clause 5: The insulated pipe of any of clauses 1 to 4, wherein thecoaxial moisture sensor is wrapped around at least a portion of theelongated tube within the at least one channel in a helical arrangement.

Clause 6: The insulated pipe of any of clauses 1 to 5, wherein thecoaxial moisture sensor extends axially along at least a portion of theelongated tube within the at least one channel in a straight line.

Clause 7: The insulated pipe of any of clauses 1 to 6, wherein theinsulating material comprises one or more of open cell foam insulation,closed cell foam insulation, fiber glass insulation, celluloseinsulation, cotton batts, and wool batts.

Clause 8: The insulated pipe of any of clauses 1 to 7, wherein thedielectric polymer material comprises one or more of nylon 4-6, nylon 6,nylon 6-6, nylon 6-12, nylon 11, polyamide-imide, polybenzimidazole,polyethersulfone, or polysulfone.

Clause 9: The insulated pipe of any of clauses 1 to 8, wherein theelectrodes comprise one or more of ruthenium, rhodium, palladium,silver, osmium, iridium, platinum, gold, copper, tin, nickel, chromium,or aluminum, or mixtures, alloys, or combinations thereof.

Clause 10: The insulated pipe of any of clauses 1 to 9, wherein amaximum outer diameter of a cross-section of the sensor along alongitudinal axis of the sensor is 0.060 inch or less.

Clause 11: A container configured to enclose objects in a low moistureenvironment, the container comprising: a top portion, a bottom portion,and sides extending between the top portion and the bottom portionthereof; and at least one coaxial moisture sensor enclosed within acavity defined by the top portion, bottom portion, and sides, thecoaxial moisture sensor comprising: a dielectric member comprising asleeve defining a center hole formed from an absorbent dielectricpolymer material; an outer electrode electrically connected with anouter surface of the dielectric member, comprising a porous sleeve forpermitting moisture to pass through the sleeve; and an inner electrodecomprising a wire extending through the center hole of and electricallyconnected with an inner surface of the dielectric member, wherein thedielectric member is in electrical contact with the first and secondelectrodes and maintains the first and the second electrodes spaced fromone another.

Clause 12: The container of clause 11, further comprising sensorelectronics operatively connected to the electrodes of the moisturesensor to measure an electrical property of the moisture sensor todetermine an amount of moisture absorbed by the dielectric member,wherein the sensor electronics comprise: a power source for applyingalternating electrical current to at least one of the first electrodeand the second electrode; and an electrical measurement deviceconfigured to measure a complex impedance (ohms) of the dielectricmember.

Clause 14: The container of clause 13, wherein the sensor electronicsfurther comprises a controller electronically connected to the powersource and to the electric measurement device, and wherein thecontroller is configured to: cause the power source to periodicallyapply the alternating current to at least one of the electrodes; receivea complex impedance measurement from the electrical measurement devicein response to the applied alternating current; and detect a presence ofmoisture in the cavity of the container based on the measured compleximpedance.

Clause 15: The container of clause 12 or clause 13, wherein thecontainer is a housing of a portable electronic device, and furthercomprising electronic circuitry of the electronic device positioned inthe cavity of the container and in electrical communication with thesensor electronics of the moisture sensor, wherein the electroniccircuitry of the portable electronic device is configured to one or moreof automatically power down, automatically save data to computer memoryof the electronic circuitry, or transmit data to a remote source whenthe measured complex impedance exceeds a predetermined value.

Clause 15: The container of any of clauses 11 to 13, wherein thecontainer comprises a liquid storage tank, and wherein the at least onemoisture sensor is positioned to detect at least one of leaks from thestorage tank and/or moisture ingress into the storage tank.

Clause 16: The container of clauses 11 to 13 wherein the containercomprises a liquid storage tank, and further comprising a controller inelectrical communication with the moisture sensor configured to: receivethe measured complex impedance from the moisture sensor; and determine aconcentration of polar and non-polar liquids in the storage tank basedon the measured complex impedance.

Clause 17: The container of any of clauses 11 to 16, wherein thecontainer comprises a liquid storage tank and a plurality ofequidistantly spaced coaxial moisture sensors on an inner surface of aside of the container, and further comprising a controller configuredto: receive the measured complex impedance from the plurality ofmoisture sensors; and determine a volume of liquid in the storage tankbased on the measured complex impedance of the plurality of moisturesensors.

Clause 18: The container of any of clauses 11 to 17, wherein the atleast one moisture sensor has a maximum outer diameter of 0.060 inch orless.

Clause 19: A method for detecting moisture in insulation surrounding apipe, the method comprising: applying an alternating electrical currentto a coaxial moisture sensor positioned within a channel extendingthrough insulation at least partially surrounding a pipe, the moisturesensor comprising: a dielectric member comprising a sleeve defining acenter hole formed from an absorbent dielectric polymer material, afirst electrode surrounding at least a portion of the dielectric member,and a second electrode extending through a portion of the center hole ofthe dielectric member; continually or periodically measuring a compleximpedance of the dielectric member with sensor electronics connected tothe first and/or the second electrodes; and determining an amount ofmoisture within the insulation based on the measured complex impedance.

Whereas particular embodiments of this invention have been describedabove for purposes of illustration, it will be evident to those skilledin the art that numerous variations of the details of the presentinvention may be made without departing from the invention as defined inthe appended claims.

The invention claimed is:
 1. An insulated pipe comprising: an elongatedtube comprising a first end, a second end, and a sidewall extendingtherebetween, the sidewall comprising an inner surface and an outersurface; an insulating member at least partially covering a portion ofthe outer surface of the sidewall of the elongated tube; and a planarmoisture sensor configured to sense moisture in the insulating member,wherein the planar moisture sensor is positioned in the insulatingmember or between the insulating member and the outer surface of thesidewall of the elongated tube, the planar moisture sensor comprising: afirst electrode comprising a flat conductive member having an innersurface and an outer surface; a second electrode spaced apart from thefirst electrode, the second electrode comprising a flat conductivemember having an inner surface and an outer surface, and a dielectriclayer comprising an absorbent dielectric polymer material positionedbetween and in electrical contact with the inner surfaces of the firstelectrode and the second electrode.
 2. The insulated pipe of claim 1,further comprising sensor electronics operatively connected to the firstelectrode and the second electrode of the planar moisture sensor tomeasure an electrical property of the planar moisture sensor todetermine an amount of moisture absorbed by the dielectric layer,wherein the sensor electronics comprise: a power source for applyingalternating electrical current to at least one of the first electrode orthe second electrode; and an electrical measurement device configured tomeasure a complex impedance (ohms) of the dielectric layer.
 3. Theinsulated pipe of claim 2, wherein the sensor electronics furthercomprise a controller operatively connected to the power source and tothe electrical measurement device, and wherein the controller isconfigured to cause the power source to periodically apply thealternating current to at least one of the electrodes.
 4. The insulatedpipe of claim 1, wherein the insulating member comprises at least one ofopen cell foam insulation, closed cell foam insulation, fiber glassinsulation, cellulose insulation, cotton batts, or wool batts.
 5. Theinsulated pipe of claim 1, wherein the absorbent dielectric polymermaterial comprises at least one of nylon 4-6, nylon 6, nylon 6-6, nylon6-12, nylon 11, polyamide-imide, polybenzimidazole, polyethersulfone, orpolysulfone.
 6. The insulated pipe of claim 1, wherein the pipecomprises multiple planar moisture sensors positioned in the insulatingmember or between the insulating member and the outer surface of thesidewall of the elongated tube.
 7. The insulated pipe of claim 1,wherein the flat conductive members of the first electrode and thesecond electrode comprise a perforated metal plate.
 8. The insulatedpipe of claim 1, wherein the flat conductive members of the firstelectrode and the second electrode comprise a conductive mesh.
 9. Theinsulated pipe of claim 1, wherein the flat conductive members of thefirst electrode and the second electrode comprise nickel plated coppermetalized polyester fabric tape, the insulating pipe further comprisinga pressure sensitive adhesive for connecting the inner surfaces of theflat conductive members to the dielectric layer.
 10. The insulated pipeof claim 1, wherein the first and second electrodes are from 0.25 inchto 0.5 inch wide.
 11. The insulated pipe of claim 1, wherein thedielectric layer is from 0.001 inch to 0.032 inch thick.
 12. A containerenclosing a cavity configured to enclose objects in a low moistureenvironment, the container comprising: a top portion, a bottom portion,and sides extending between the top portion and the bottom portionthereof, each of the top portion, the bottom portion, and the sidescomprising an inner surface and an outer surface; and a planar moisturesensor mounted to and extending over at least a portion of at least oneof the inner surface or the outer surface of at least one of the topportion, the bottom portion, or the sides, the planar moisture sensorcomprising: a first electrode comprising a flat conductive member havingan inner surface and an outer surface; a second electrode spaced apartfrom the first electrode, the second electrode comprising a flatconductive member having an inner surface and an outer surface, and adielectric layer comprising an absorbent dielectric polymer materialpositioned between and in electrical contact with the inner surfaces ofthe first electrode and the second electrode.
 13. The container of claim12, further comprising sensor electronics operatively connected to theelectrodes of the planar moisture sensor to measure an electricalproperty of the planar moisture sensor to determine an amount ofmoisture absorbed by the dielectric layer, wherein the sensorelectronics comprise: a power source for applying alternating electricalcurrent to at least one of the first electrode or the second electrode;and an electrical measurement device configured to measure a compleximpedance (ohms) of the dielectric layer.
 14. The container of claim 13,wherein the container is a housing of a portable electronic device, thecontainer further comprising electronic circuitry of the electronicdevice positioned in the cavity of the container and in electricalcommunication with the sensor electronics of the planar moisture sensor,wherein the electronic circuitry of the portable electronic device isconfigured to one or more of automatically power down, automaticallysave data to computer memory of the electronic circuitry, or transmitdata to a remote source when the measured complex impedance (ohms)exceeds a predetermined value.
 15. The container of claim 12, whereinthe container comprises a liquid storage tank, and further comprising acontroller in electrical communication with the moisture sensorconfigured to: receive the measured complex impedance (ohms) from theplanar moisture sensor; and determine a concentration of polar andnon-polar liquids in the storage tank based on the measured compleximpedance (ohms).
 16. The container of claim 12, wherein the flatconductive members of the first electrode and the second electrodecomprise a perforated metal plate.
 17. The container of claim 12,wherein the flat conductive members of the first electrode and thesecond electrode comprise nickel plated copper metalized polyesterfabric tape, the insulating pipe further comprising a pressure sensitiveadhesive for connecting the inner surfaces of the flat conductivemembers to the dielectric layer.
 18. The container of claim 12, whereinthe first and second electrodes are from 0.25 inch to 0.5 inch wide. 19.A method for detecting moisture in insulation surrounding a pipe, themethod comprising: applying an alternating electrical current to aplanar moisture sensor positioned in insulation at least partiallycovering an outer surface of the pipe, the planar moisture sensorcomprising: a first electrode comprising a flat conductive member havingan inner surface and an outer surface; a second electrode spaced apartfrom the first electrode, the second electrode comprising a flatconductive member having an inner surface and an outer surface, and adielectric layer comprising an absorbent dielectric polymer materialpositioned between and in electrical contact with the inner surfaces ofthe first electrode and the second electrode; continually orperiodically measuring a complex impedance (ohms) of the dielectriclayer with sensor electronics connected to the first and/or the secondelectrodes; and determining an amount of moisture within the insulationbased on the measured complex impedance (ohms).
 20. The method of claim19, further comprising generating an alert when the determined amount ofmoisture within the insulation exceeds a predetermined threshold value.